1. Field of the Invention
The present invention relates to a light emitting diode (LED) tube and more particularly to an LED tube having long internal creepage distances.
2. Description of Related Art
LEDs have features of small volume, high luminous efficiency and long service life. Thus, LED tubes using LEDs as light sources have become more and more common.
With reference to FIG. 18, a conventional LED tube has a heat dissipating seat 60, an LED light board 70, a translucent tube shell 80 and two caps 90.
The heat dissipating seat 60 is semi-cylindrical and has a rectangular flat surface, a convex surface, multiple fins 61 and two slide tracks 62. The rectangular flat surface has two opposite long sides and two opposite short sides. The multiple fins 61 are formed concave on the convex surface, and the two slide tracks 62 are respectively formed on the two long sides of the flat surface.
The LED light board 70 is rectangular and has two opposite long sides, two opposite short sides vertically connected to the two long sides, four electrical connecting parts 71 and multiple LED units 72. The two long sides of the LED light board 70 are slidably mounted in the two slide tracks 62 respectively. Thus, the LED light board 70 is mounted on the flat surface of the heat dissipating seat 60, and the two short sides of the LED light board 70 are respectively in alignment with the two short sides of the flat surface. Each two of the four electrical connecting parts 71 are mounted on the LED light board 70 and near a corresponding short side of the LED light board 70. The multiple LED units 72 are mounted at intervals on the LED light board 70 in a longitudinal direction of the LED light board 70.
The translucent tube shell 80 is semi-cylindrical and is connected to the heat dissipating seat 60 to form a tube body, wherein the translucent tube shell 80 faces the multiple LED units 72 of the LED light board 70.
Each cap 90 is sleeved on a corresponding end of the tube body and has two electrode pins 91 respectively and electrically connected to two of the electrical connecting parts 71 that are adjacent to the corresponding end.
When the LED tube is mounted in a lamp holder and is switched on, the LED light board 70 obtains power through the four electrode pins 91 of the two caps 90 and glows by the multiple LED units 72. Heat produced by the functioning LED light board 70 is conducted to the heat dissipating seat 60 and further dissipated by the multiple fins 61.
With reference to FIG. 19, the two opposite short sides of the LED light board 70 are aligned with the heat dissipating seat 60, wherein the electrical connecting parts 71 are mounted near the short sides of the LED light board 70, that is, the electrical connecting parts 71 are mounted near the heat dissipating seat 60. Besides, the electrical connecting parts 71 are also mounted near the two slide tracks 62. The electrical connecting parts 71 are electrically conductive elements, and the heat dissipating seat 60 and the two slide tracks 62 are both made of metal, which is highly conductive. A creepage distance d1 between the electrical connecting part 71 and the two slide tracks 62 is relatively short. When the LED tube functions, the electrical connecting parts 71 obtain a high voltage power from the caps 90. A surface of the LED light board 70 around the electrical connecting parts 71 may be electrically polarized due to the high voltage power obtained by the electrical connecting parts 71. The electrical connecting parts 71 and the slide tracks 62 may be conducted through the polarized surface causing short-circuit between the electrical connecting parts 71 and the slide tracks 62 damaging the LED tube.
Furthermore, each cap 90 is only sleeved on a corresponding end of the tube body consisting of the heat dissipating seat 60 and the translucent tube shell 80, that is, a connection between each cap 90 and the tube body is not stable. When an unexpected force is applied on the LED tube, the caps 90 are to rotate easily and cause a deviation of the illumination angle of the LED tube.